The present invention relates to the reading of an image from an object by scanning the object, and more particularly to a method of and an apparatus for correcting an image signal, while reading an image based on the image signal which is produced by scanning an object on which image information is recorded, with a light beam, and photoelectrically detecting light bearing the image information, by substantially subtracting a noise component contained in the light beam from the image signal to remove an image noise component from the image signal, which would otherwise be generated by the noise component in the light beam.
Heretofore, there have widely been employed a light beam scanning reading apparatus for scanning an object on which image information is recorded, with a light beam which is deflected in a main scanning direction by a light deflector such as a galvanometer mirror, a rotating polygon, a hologram scanner, or the like, simultaneously moving the object relatively in an auxiliary scanning direction which is substantially normal to the main scanning direction, for thereby scanning the object two-dimensionally, and photoelectrically detecting light bearing the recorded image information, which is emitted from the object, to read the image information as an electric signal. One example of such a light beam scanning reading apparatus is a radiation image information reading apparatus in which a stimulable phosphor sheet with radiation image information recorded thereon is scanned by stimulating light such as a laser beam or the like to emit light bearing the recorded radiation image information, and the emitted light is photoelectrically detected to produce an image signal.
The stimulating light in the radiation image information reading apparatus is generated by a light source such as a gas laser or a semiconductor laser, for example. As shown in FIG. 1 of the accompanying drawings, the laser produces laser noise .DELTA.P in the vicinity of a given laser output level Po. The laser noise .DELTA.P causes a level So, corresponding to the laser output level Po, of light PSL emitted from the stimulable phosphor sheet to vary by .DELTA.S. Therefore, the generated image signal contains image noise corresponding to the variation .DELTA.S in the emitted light PSL. As a result, an image reproduced from the image signal becomes inaccurate.